1. Field of the Invention
The present invention relates to a photoconductor for electrophotography, and particularly to a photoconductor for electrophotography which contains a novel azo or disazo compound in the photosensitive layer thereof formed on an electroconductive substrate.
2. Description of the Prior Art
Photosensitive materials which have heretofore been used in photoconductors for electrophotography include inorganic photoconductive substances such as selenium and selenium alloys, dispersions of inorganic photoconductive substances such as zinc oxide and cadmium sulfide in resin binders, organic polymeric photocondutive substances such as poly-N-vinylcarbazole and polyvinylanthracene, organic photoconductive substances such as phthalocyanine compounds and bisazo compounds, and dispersions of such organic polymeric photoconductive substances in resin binders.
Photoconductors are required to have the characteristics of maintaining a surface electric charge in the dark, generating an electric charge upon receiving light, and transporting an electric charge upon receiving light. They are classified into two photoconductor types namely, so-called monolayer type photoconductors, and so-called laminate type photoconductors. The former comprises a single layer having all of the above-mentioned three characteristics, and the latter comprises functionally distinguishable laminated layers, one of which contributes mainly to the generation of electric charge, and another of which contributes to the retention of surface electric charge in the dark and electric charge transportation upon receiving light. An electrophotographic method using a photoconductor of the kind as mentioned above, is for example the Carlson's system and is applied to image formation. The image formation according to this system comprises the steps of subjecting a photoconductor in the dark to corona discharge to charge the photoconductor, illuminating the surface of the charged photoconductor with imagewise light based on a manuscript or copy bearing, e.g., letters and/or pictures to form a latent electrostatic image, developing the formed latent electrostatic image with a toner, and transferring the developed toner image to a support such as a paper sheet to fix the toner image on the support. After the toner image transfer, the photoconductor is subjected to the steps of removal of the electric charge, removal of the remaining toner (cleaning), neutralization of the residual charge with light (erasure), and so on to be ready for reuse.
Photosensitive members for electrophotography in which use is made of an organic material(s) have recently been put into practical use by virtue of the advantageous feature(s) of the organic material(s), such as flexibility, thermal stability, and/or a film forming capacity. They include a photoconductor comprising poly-N-vinylcarbazole and 2,4,7-trinitrofluoren-9-one (disclosed in U.S. Pat. No. 3,484,237), a photoconductor using an organic pigment as the main component (disclosed in Japanese Patent Laid-Open No. 37,543/1972), and a photoconductor using as the main component a eutectic complex composed of a dye and a resin (disclosed in Japanese Laid-Open Patent Application No. 10,785/1972). A number of novel hydrazone compounds have also been put into practical use for photosensitive members.
Although organic materials have a number of advantageous features mentioned above with which inorganic materials are not endowed, the fact is that there have been obtained no organic materials fully satisfying all the characteristics required of a material to be used in photoconductors for electrophotography at present. Particular problems involved in organic materials have been concerned with photosensitivity and characteristics in continuous repeated use.